Petroleum hydrocarbon feedstocks such as petroleum crudes, gas oil, etc., are subjected to various processes in order to isolate and separate different fractions of the feedstock. For example, in refinery processes, the feedstock is distilled so as to provide light hydrocarbons, gasoline, naphtha, kerosene, gas oil, etc.
The lower boiling fractions are recovered as an overhead fraction from distillation zones. The intermediate components are recovered as side cuts from the distillation zones. The fractions are cooled, condensed, and sent to collecting equipment. No matter what type of petroleum feedstock is used as the charge, the distillation equipment is subject to the corrosive attack of various halide-based acids such as HCl.
HCl is probably the most troublesome corrosive material and may be formed by hydrolysis of calcium and magnesium chlorides originally present in the brines produced concomitantly with the feedstock.
Halide-based corrosion caused in such refinery systems may occur on the metal surfaces of fractionating such as crude towers, trays within the towers, heat exchangers, etc. The most troublesome locations for corrosion are the overhead of the distillation equipment which includes tower top trays, overhead lines, condensers and the top pump around exchangers. It is usually within these areas that water condensation is formed or is carried along with the process stream. The top temperature of the fractionating column is maintained close to or above the boiling point of water. The condensate formed after the vapor leaves the column may contain significant concentration of the halide-based acids mentioned above. This high concentration of acidic components renders the pH of the condensate highly acidic and, as such, dangerously corrosive.
Petrochemicals, such as chlorinated hydrocarbons and olefin plant fluids, such as deethanizer bottoms, are also subjected to corrosive attack of halide containing acids both during the product storage and shipment steps as well as during the heat treatment steps employed in petrochemical synthesis, product isolation and purification. For example, in the manufacture of vinyl resins, such as poly(vinyl)chloride, ethylenedichloride (EDC) hydrocarbon is commonly dehydrochlorinated over a barium catalyst at about 500.degree. C. (932.degree. F.) to form the desired PVC product. However, chlorides present in the EDC charge or those produced as a by-product in the PVC synthesis can cause severe corrosion of distillation equipment, heat exchangers and product recovery equipment.
Accordingly, there is a need in the art to provide an effective halide scavenger that is capable of reducing the halide content of petroleum feedstocks and petrochemicals both during the shipment and storage stages of same as well as during the heat processing thereof (such as at temperatures of from about 100.degree. F. to 1000.degree. F., more particularly 200.degree. F.-1000.degree. F.) to minimize the deleterious corrosive effects of the halides in such mediums.